EEPROMs are known as semiconductor memory devices wherein the data cells in the memory array can only be accessed sequentially. Because this type of semiconductor memory device is relatively inexpensive, it is used as a memory device for storing data pertaining to the quantity of remaining consumable materials or the quantity of consumable materials used. Moreover, there are also semiconductor memory devices that have been produced that have multiple data storage areas, for example, EEPROM areas and masked ROM areas. In semiconductor memory devices that have multiple data storage areas, the use of masked ROM area has the benefit of eliminating the need for writing read-only data to the semiconductor memory device.
However, sequential access semiconductor devices, when provided with a single data storage area that has an area that can be written that is smaller than the read-only area cannot return to the starting address of the writeable area without counting up until the final address of the read-only area first. The result is a problem in that more time is required in the data writing process than in reading out data.
Moreover, because in a semiconductor memory device the address at which access is started is typically specified using an address code, and semiconductor memory devices that are provided with a plurality of data storage areas, address codes must be provided for each of the data storage areas, which tend to increase the scope of the circuit structure.